DOWNLOAD Panasonic KX-MB1900RUB / KX-MB1900RUW Service Manual ↓ Size: 15.99 MB | Pages: 127 in PDF or view online for FREE

25

KX-MB1900RUB/KX-MB1900RUW

The scanning block of this device consists of a control circuit and a CIS (contact image sensor), and AFE(Analog Front End) include
A/D Converter.

When an original document is inserted and the start button pressed, pin A3 of IC300 goes to a low level and the transistor Q518
turns on.
This applies voltage to the CIS. The CIS is driven by each of the CCDSH, CCDCLK signals output from IC300, and the original
image illuminated by the LED to output an analog image signal.
The analog image signal is input to the AFE on VINP(20pin of IC503) and converted into 16-bit data by the A/D converter inside
IC503. Then this signal undergoes digital processing in order to obtain a high-quality image.

26

KX-MB1900RUB/KX-MB1900RUW

1. Functions

All driving forces of printer engine part are supplied by this engine motor.
Engine motor is controlled so as to rotate at constant speed during printing and copying.

2. Motor operation

<Start operation>
In order to start the motor rotation, following 3 signals are supplied from IC300.

1. SS signal (Output pin: Pin B12/Output Signal: "H")
When this signal is inverted by transistor Q502 and becomes "L", motor recognize this signal as "start" signal.
2. Clock signal (Output pin: Pin A12/Output Signal: Pulse)
Pulse frequency :approx. 2.2KHz (at normal printing speed)
Pulse frequency :approx. 1.1KHz.(at half printing speed)
This signal is also inverted by transistor Q525, and supplied to motor as "clock" signal.
3. Brake signal (Output pin: Pin C12/Output Signal: "H")
When this signal is inverted by transistor Q526 and becomes "L", motor recognize this signal as "brake off" signal.

When motor reaches constant speed, "L" signal is supplied from motor to IC300 pin D12 as "Lock detect (LD)" signal.
If "LD" signal does not becomes "L" within predetermined period after "SS" signal becomes "H",  or if "LD" signal becomes
"H" during rotation, it is judged that motor Error occurred.

Timing Chart of Start operation

27

KX-MB1900RUB/KX-MB1900RUW

<Stop operation>
In order to stop the motor rotation, following 2 signals are supplied from IC300.
1. SS signal (Output pin: Pin B12/Output Signal: "L")
When this signal is inverted by transistor Q502 and becomes "H", motor recognize this signal as "stop" signal.
2. Brake signal (Output pin: Pin C12/Output Signal: "L")
When this signal is inverted by transistor Q526 and becomes "H", motor recognize this signal as "brake on" signal.

Timing Chart of Stop operation

General

Scanner motor drive circuit is consist of motor current control circuit ,FB (Flat Bed) motor driver and OCP (Over Current Protection)
circuit.

1. Circuit explanation

According to the scan speed, each motor current is controlled for appropriate value.
When scan speed is low, motor current is reduced to prevent the vibration during motor rotation. 
When scan speed is high, motor needs much driving force. so much current should be supplied.

28

KX-MB1900RUB/KX-MB1900RUW

For the control of motor current, Vref voltage of each motor driver is controlled.
When Vref voltage is high, motor current is increased, and the voltage is low, motor current is reduced.
In order to control the Vref voltage, PWM pulse is supplied from IC300 pin D8.
PWM pulse is inverted by Q521 and integrated by R533, R534, and C509, then converted to DC voltage.

This DC voltage is supplied to Vref pin of each motor drivers.
When duty of PWM pulse is high, Vref voltage is decreased and when duty is low, Vref voltage is increased.

For FB motor, motor current is controlled approx. 0.1A-0.25A.

2. Circuit diagram of current control and OCP circuit

3. Timing chart

Following timing charts are the example when PWM pulse duty are approx 9% and 45%.